Kiln and heating furnace



Dec. 31, 1935. A. M. ROSSMAN KILN AND HEATING FURNACE Filed Sept. 28, 1933 3 Sheets-Sheet l 31, 1935. A. M. R ssMAN 2,026,066

KILN AND HEATING FURNACE Filed Sept. 28, 1953 3 Sheets-Sheet 2 am Wm Dec. 31, 1935. A. M. ROSSMAN KILN AND HEATING FURNACE Filed Sept. 28, 1933 3 Sheets-Sheet 3 nwE/vm W/T/VESS:

Patented Dec. 31, 1935 UNETED STATES KILN AND HEATING FURNACE Allen M. Rossman, Wilmette, 111., assignor to Rossrnan Engineering Company, Chicago, 111.,

a corporation of Illinois Application September 28,

' 30 Claims.

The present invention relates in general to kilns and heating furnaces and particularly to a continuous kiln or heating furnace which operates on fundamentally correct principles of gas and air flow.

Present designs of kilns and heating furnaces in which the wares pass successively through heating and firing zones and then in some cases through a cooling zone, in which the air for combustion is heated as it cools the hot wares, operate on the principle of a substantially horizontal flow of air and gases. Inherent in such a system of flow is the tendency of the hotter gases to seek the upper part of the chamber while the cooler gases flow through the lower portion, this Stratification resulting in uneven temperature distribution through the wares and hence, non-uniform heating.

The downdraft flow of hot gases and the updraft flow of air have long been recognized as the only systems of flow which act inherently to set up a uniform distribution of temperature throughout the ware, furnace or kiln. This is due to the fact that in the zone of hot waste gases, the hotter passages, acting as stacks, offer more resistance to the down flow of hot gases than do the cooler passages and thereby raise their temperatures. Likewise, in the zone of cold air, the hotter passages offer less resistance to the upflow of air than do the cooler passages and thereby lowers their temperatures. Thus, in each of these cases, the direction of flow tends inherently to so distribute the volumes of flow that they smooth out any differences in temperature and thereby cause the temperature to equalize throughout the entire volume of the ware.

Many attempts are being made in present continuous type kilns and heating furnaces to direct the air and gas flow in their proper directions, but the shapes and designs of most furnaces and kilns prevent these principles from being anything but approximately carried out. In the present invention, designs are disclosed in which these principles of downdraft flow of gases and updraft flow of cold air are strictly adhered to in a continuous kiln or heating furnace. The kiln or furnace consists of a plurality of refractory lined unit heating chambers, each unit being mounted on flanged whee-l trucks to form a car. The cars are placed in line and their interiors are connected in series by means of interconnecting ducts to form a continuous duct system.

Firing takes place in one or more cars of the train and the gases of combustion flow through 1933, Serial No. 691,278

other cars in succession, giving up some heat in each car to the product being heated therein. When the heating process is completed in the first car of the train, it is disconnected, and a cold car is added to the end of the train and the whole train is pushed ahead one car length.

Any of the known methods can be used for moving the train, such as a locomotive, Windlass and cable, hydraulic pusher, etc.

This system can be used in applications which require the continuous type of furnace or kiln, such as the billet heating furnace and the tunnel kiln.

In the case of a kiln, the cold air is admitted to the first car and the fuel is burned in one or more of the cars further down the line. The gases of combustion pass successively through all the following cars and are discharged from the last car. By this method the cars which have pased the burners preheat the air as the hot ware is cooled off: the cars at the burners carry the highest temperature and the cars approaching the burners are gradually heated up by the waste gases as they progress toward the burners.

One object of this invention relates to the uniform heating of a product by down draft circulation of hot gases instead of passing the gases through the product in a horizontal direction as in present tunnel kilns and continuous furnaces, in which stratification of gases causes non-uniform heating.

A further object of the present invention relates to a car type progressive kiln in which the ware is not only heated by a downdraft system of flow of hot gases, but is also cooled by an updraft system of flow of the air for combustion in the kiln, thus providing for maximum efficiency and uniform temperature distribution throughout the entire process.

Another object of this invention has to do with a continuous heating furnace or kiln in which the path of the gases can be increased or decreased in length to accommodate different classes of ware which require different temperature conditions.

Another object has to do with a continuous heating system which can be furnished in units which are factory made and assembled and which can be held out of service for maintenance without interrupting the heating process.

Other objects and advantages will become apparent from the further explanation and disclosure.

I will now describe several embodiments of car of the mufile type.

Figure 6 is a plan section taken along line 6-8 in Figure 5.

Figure 7 is a plan section taken through line 1-'l in Fig. 5.

Figure 8 is another embodiment of the present invention in plan view.

Figure 9 is an elevation of the embodiment of Figure 8.

Figure 10 is a longitudinal section of one of the cars of the embodiment of Figures 8 and 9.

Figure 11 is a transverse section of a car taken along the line HIl in Figure 10.

Figures 1 and 2 show a continuous kiln built according to the principles of this invention, consisting of a train of cars l to 4 inclusive. Each car consists of a refractory lined chamber which is mounted on a fiat car 6. The flat car moves on wheels I which are adapted to run on a track 8. The cars are assembled in a train and are spaced at the proper intervals by means of buffers 9 on each car.

Each kiln unit 5 is constructed with a steel shell or jacket 19, which is shown in Figure 3. The'jacket is lined with any suitable heat insulation. A comparatively thin but effective wall construction consists of a layer of magnesia block insulation H next to the steel, and then an inner layer of high temperature insulating brick l2. Brick of this class, which has but recently been placed on the market, will resist temperatures of nearly 3000 F., is very light in weight, and has an insulating value about four times that of common firebrick.

A circular form of chamber 5 with a dome shaped roof is preferable because of its simple and sturdy construction, as the entire structure can be held together by jacket l0, reinforced by bands IS. The chamber 5 is split on a horizontal plane in its lower half for the purpose of drawing and setting the ware. This line of partition it is sealed against atmospheric leakage by a seal l5, comprising a trough I6, attached to the lower wall of the chamber, and a lip ll attached to the upper wall. Both lip and trough extend continuously around the chamber. The trough is filled with a sealing medium such as sand, into which the lip dips.

LThe upper portion of the chamber can be lifted off by means of suitable eyebolts or lugs I8 which are attached to the steel jacket.

The cars are interconnected by means of short sections of duct. Each car has an upper duct I9 and a lower duct 20. The upper duct connects into the kiln chamber at the top and bends downward at right angles to meet the lower duct of the adjoining car, which leaves the bottom of the chamber and bends upwards.

When in operation, the ducts are sealed at the clearance crack by means of another sand seal 21. Although there are several methods of sealing this crack, my preferred method is shown in cross-section in Figure 4. A trough 22, filled with sand or other sealing material, encircles the ehd of the upward extending lower duct 20, into which dips a sealing lip 23. This lip, instead of being fastened to the duct I9, is movable vertically and has another lip portion 24 which dips into another sealing trough 25 attached to the duct It. The purpose of this form of seal is to permit the cars to be lined up in a train with the interconnecting ducts which the lips 23, 24 can be dropped, so that the upper portion 2Q dips into the trough 25 on the upper duct, and the lower portion of the lip 23 dips into the trough 22 on the lower duct,

in register, after thereby sealing the clearance crack between the 15 ducts against atmospheric leakage. When the cars are being fired, they will be set on a straight track so that as the train is moved along there is no lateral movement between the duct sections. Instead of a straight track, one of uniform curvature would be suitable, the ducts be ing arranged to coincide when the cars are on such a track.

Air is supplied to the train by a forced draft fan 26, which is driven by a motor (not shown) or other suitable means of propulsion connected tothe drive shaft 21'. The fan is connected to the inlet duct 29 of the first car by means of a movable duct, section 23, which can be rotated into position and sealed against leakage in the 30 mamier shown in Figure 4. The movable duct section 28 would then take the place of the upper duct 59 in Figure 4. The movable section 28 is rotatable at its connection with the fan and it can be designedto be flexible. sealed by means of another fluid seal 29.

The cold. air flows through several of the cars represented by the car indicated by the reference numeral I, in which it is heated up by contact with the hot ware in the cars. place in one or more of the cars 2, 3. The fuel, and, if it is used, the atomizing medium is supplied through fiexible pipes 39 which connect into burners 3| which are inserted through holes in one or both sides of the car. closed by plugs or covers 3i when not in use. The fuel is burned in a space between the ware and the roof which is provided for that purpose. The hot gases of combustion passs down through The joint is Firing takes 40 The holes are the Ware and leave the car at the bottom by the 5) outlet duct 29, through which they flow upward and through the inlet duct is of the adjoining car. The gases then flow downward through each car in succession until they leave the last car 4 through the outlet duct 26 and through another movable section of duct 32 similar to that connected to the forced draft fan connecting the outlet duct of the last car with the intake 33 of the induced draft fan 34. A car in each of the heating, firing, and cooling zones is shown brokon to indicate that there are an indefinite number of cars in each zone. A seal 35 closes the juncture between the movable duct section and the fan intake 33. The induced draft fan 84 6 discharges to the stack 36.

Duct connections are so arranged that the hot gases flow downward and the cold air flows upward through the wares.

In order to change the direction of flow from Figures 1 and 2 show one method of accomplishing this reversal and Figures 8 and 9 show another method.

In Figures 1 and 2 this reversal is accomplished by rotating each car as it leaves the firing zone 180 on a turntable 39. The turntable comprises a length of track 50 carried on a framework 4! which rotates on wheels 42 which roll on a circular track 43.

A short length of duct 31 making an angle of 180 and mounted on a truck 38 is interposed between the cars in the firing zone and those in the cooling zone for the purpose of interconnecting the two adjacent upper interconnecting ducts IS on the first car I in the cooling zone, which has already been reversed, and the last car 2 in the firing zone, which is the next car to be reversed.

The sequence of operations in switching cars is as follows: The burners are moved from the car 2, which is about to leave the firing zone, to the car 4, which is about to enter the firing zone. Firing is stopped and the draft is interrupted. The car 2, which is about to leave the firing zone, and the short piece of interconnecting duct 3'! are rotated 180 on the turntable 39, the disconnected duct ends being covered during this operation to prevent cold air from entering the cars. This reverses the positions of the ducts on the car 2, and its lower interconnecting duct 29 can be coupled to the upper duct i9 of the adjacent car I, flow through the car from downdraft to updraft. The 180 interconnecting elbow 31 is then connected to the next car 3 in thefiring zone. The air duct 28 and the exhaust duct 32 at the opposite ends of the train are disconnected. A car of fresh ware is pushed up to the rear end, the whole trainis pushed ahead one car length, and a car of finished ware is taken off the front end. The air duct 28 and the exhaust duct 32 are reconnected and firing is resumed.

The interruption of operations for the purpose of making these changes in connections will have but little effect on the operation-of the kiln for several reasons, viz: it occurs but once in one to four hours; there is little tendency for the gases to migrate during this period, except that the cooler gases will gravitate to the floors and the hotter gases will rise toward the roofs in each car; last, but most important, conditions of temperature equilibrium are re-established immediately after the ducts have been reconnected and draft conditions are re-established.

Figures 3 and 5 are sectional elevations showing details of construction of car units built respectively on the direct fired and on the muflle kiln principles.

Figure 3 shows a direct fired car in which the ware 45 is set in the chamber extending from the opening of lower duct 20 to the opening of the upper duct l9. The ware is set on a foundation 46 of refractory pieces which are spaced apart to allow the hot gases to collect beneath the were and tofiow out through the interconnecting duct-20. The space 41 between the ware and the roof 48 is the space for combustion in the cars in the firing zone, and it is into this space that the fuel discharged from burners 3| is directed.

The upper interconecting duct I9 is fastened to the upper part of the chamber and is removed with that part when the ware is ready to be drawn. The lower duct 20, which is connected to the lower part of the chamber 5, remains on the car.

Figure-5-showsa car built on the muflle-princithereby changing the direction of ple in which the ware 50 is set within a secondary compartment 5|. This principle is used in burning terra cotta, enameled bricks, and other wares which must be protected from contact with the gases of combustion. 5

In this embodiment, the ware is set on foundation pieces 55, which are laid on a circular refractory floor 52. This floor is supported on a raised portion 53 of the truck frame 6. The chamber 5 in this case is all in one unit, 10' which is lowered down over the ware and the circularfioor and rests on the truck framework 6. The sealing between the two members is formed by a sand seal 54, consisting of a sand filled trough 55 extending around the edge of 15 the floor and a lip 56 attached to the base 51 of the chamber which dips into the trough. In this manner the interior compartment 5|, in which the ware is set, is sealed against both the furnace gases and the atmosphere. 20-

Figures 5, 6, and 7 show the method of constructing the chamber, Figure 6 being a plan section taken along line 6-45 in-Figure 5, and Figure 7 is a plan section taken along line 11' in Figure 5. 25

The inner compartment 5| is formed of hollow tile members 58 which line the walls of the main chamber 5 and extend from the upper duct opening 19 substantially to the lower duct opening 26. The hollow tiles are supported on a 80- circular refractory inner wall 59. The lower portion 65 of the outer wall of the chamber 5 is flared out to form an enlarged annular space 6|, into which the lower connecting duct 26 connects. The ducts i9, 25 can be slightly flattened, 36 as indicated, thereby reducing the height and distance between cars.

The tiles in the top layer are provided with a skew-back portion 64 which forms the supporting base for the inner dome-shaped roof 62. A 40 metal band 63 around the outside of the chamber 5 at the level of the upper tiles supports the thrust of the inner roof.

The hot gases of combustion flow downwards from the combustion space 47, through the hol- 45 low tiles, 58 which surround the inner compartment 5|, and into the annular space 5i at the bottom where they collect, and leave by the interconnecting duct 20.

Heat is transferred to the walls and roof of the inner compartment from the hot gases'and from there to the ware by radiation and convection.

In most continuous kiln operations, especially in the case of kilns of the mufile type, it is nec- 55 essary to dry the ware and also to oxidize the impurities in the clay before the ware is burned. This operation requires a flow of hot air over the ware and in most present type tunnel kilns this fiow is obtained by by-passing hot air from 60' the cooling zone to the dryers.

For this purpose I have provided an opening 65 in the top of each of the upper connecting ducts l9, as shown in Figures 3 and 5. Normally, this opening is covered by a refractory 65 lined cover 66, and the line of separation is sealed by means of a sand seal 67 of the type previously described herein.

Hot air is drawn from this bypass opening through a movable section of duct 58 which fits over the opening 65 and is sealed thereto. The section of duct rotates out of position during movement of the cars, the joint between movable and stationary members of this duct 68 being sealedby another sand seal 61-". A damper 69 controls the amount or air bypassed through this duct for use in drying and oxidizing the ware.

As each car is provided with a bypass opening, the bypass duct 68 can be located to tap off any car in the cooling zone; the nearer this duct is located to the burners, the hotter will be the air drawn off.

Present type tunnel kilns are operated with large quantities of excess air to counteract the natural tendency of the gases to build up horizontal zones oftemperature strata in the preheating section. The heating is then regulated by drawing these gases oif at a number of distributed points along the preheating section. In the present invention, the downdraft flow of gases prevents stratification and therefore permits the volume of excess air to be greatly reduced. In the muffle kiln and in the open type kiln, in which the ware is enclosed in saggers or is otherwise protected against a too rapid change in temperature, the temperature curve is regulated by inserting burners at points where the temperature. of the gases tends to drop too rapidly, and giving a slight boost to the temperature of the smaller volume of gases.

The latter method of operating is more economical in fuel consumption than the former, and is a practical method because each car has its own combustion chamber and because any local differences of temperature are quickly equalized by the downdraft system of gas flow.

Figures 8 and 9 show another embodiment of this invention in which is shown a second method of reversing the direction of flow so that the air will have an updraft flow and the waste gases will have a downdraft flow. In this embodiment, rectangular instead of circular chambers are illustrated.

Figure 10 is a longitudinal section taken through one of the cars and Figure 11 is a transverse section.

Referring to Figures 8 to 11 inclusive, each car has two inlet ducts H1, H and two outlet ducts l2, 33. One of the inlet ducts 1B and one of the outlet ducts l2 connect into the top of each car, while one inlet duct 'H and one outlet duct ?3 connect into the bottom of each car. The ducts are so arranged that when a train of cars are coupled together the upper outlet duct of each car connects with a lower inlet duct of the adjoining car at each end of the car and vice versa. The ducts can be joined and sealed by means of fluid seals 2! in the manner described in connection with Figure 4.

The means by which the flow of air and gases is reversed is shown in Figures 10 and 11. The openings of each of the lower ducts H, l3 into the kilns are provided with a shut-01f damper i4, '55 which are shown as sliding dampers operated by removable handles inserted through holes in the sides of the car covered by covers 36, W. The dampers slide between the end Wall of the furnace and a refractory supporting structure 18 which serves as a guide for the damper and a support for the ware or product of the kiln. It is made in the form of checkers or other form having openings to allow the gases to collect beneath the ware and flow out through the lower exit duct 13.

This supporting structure is also desirable from the standpoint that it supports the ware above the duct opening, thereby providing better burning of the ware at the bottom.

The walls and roof in this embodiment sepin the upper part of the kiln 83.

arate from the lower portion 19 of the kiln at a line just above the dampers and supporting checkers. A fluid seal l6 closes this line of separation against atmospheric leakage.

' The path of the air and gases is indicated by 5 arrows. From the forced draft fan 26 the air is forced through the movable duct section 28, which in this case is adapted to connect with the lower inlet duct 'H. The air enters the bottom of the first car and rises upwards through the ware, whereby heat is transferred from the ware'to the air. The damper i4 is moved away from the duct opening. The upper inlet duct 10 is closed oif by means of any suitable plug or cover (not shown) over the end of the duct to prevent the air from blowing out of this duct.

As the lower outlet duct 13 is closed off by the damper 15, the air leaves the kiln 8| by the upper outlet duct 12 and flows down through the 20 inlet duct H of thesecond car 82. As the damper M in this car is also in the open position, the air enters the bottom of the car 82. In this car 82 the flow must be reversed so that in the car 83, in which firing is taking place, the air will be introduced at the top of the car with thefuel.

To accomplish this reversal, the outlet damper T5 of the second car 82 is set in the open position, allowing the air to flow across the bottom 'of the kiln 82 and out through the lower outlet duct 13, whereby it is forced into the top of the next car 83 through the upper inlet duct 10. The air is prevented from flowing up through the car 82 and out through the upper outlet duct 1 by the damper 14 in the third car 83, which is in the closed position.

The air unites with the fuel, which is injected by means of one or more burners 3! supplied by flexible pipes 3d, and combustion takes place 40 The hot gases flow downward through the ware in the kiln, the draft being created by the fans 26, 34. As the outlet damper T5 in the bottom of the kiln 83 is open, the gases pass to the top of the next car Bdthrough the outlet duct 13 and the inlet duct 10.

In the remainder of the cars in the train the flow is downward through the ware in each car. In this illustration I have shown two cars 83, 84 in the firing zone and one car 85 in the heating zone, but it is understood that there will normally be many more cars in each zone.

. After flowing downthrough the last car 85, the gases leave by the lower duct 73. The upper outlet duct 12 is closed to the atmosphere by any suitable cover which can be fastened over the duct opening.

The gases are drawn by the induced draft fan 34 through the movable duct section 32, which is' connected to the end of the lower outlet duct 13 and discharged up the stack 35.

It is evident that as each cold car is placed at the end of the train the inlet damper M should be closed and the outlet damper I5 should be open. When the car is moved past the firing position, the inlet damper 14 is opened by pushing it over by means of a removable rod. As the car is moved to the next position, the other damper i5 is pushed over, thereby closing the lower outlet duct.

The principal advantages of this kiln over present types of tunnel kilns-are listed in the following summary:

1. The downdraft flow of hot. gases and the'75 updraft flow of air through the ware give a more uniform distribution of temperature through the ware, a more uniform product, and a more effective transfer of heat to the ware than is possible in present type tunnel kilns. This uniformity is not upset by slight variations in the setting of the ware.

2. The uniform temperature distribution causes the ware to shrink evenly and hence avoids danger of toppling of the ware during burning. The usual cause of toppling is uneven shrinkage of the ware, especially shrinkage of the bottom and sides ahead of the interior of the stack of ware.

3. Toppling of the ware in one car does not entail the costly'shut-down of two to four weeks that is sometimes experienced with the tunnel kiln, because the ware comes to rest against the sidewalls of the car.

4. The maximum height of ware on the car is limited by consideration of stability and weight rather than by the temperature difference between the top and the bottom of the stack of ware, or by the taking of undue precautions against the danger of toppling.

5. The minimum height of ware on the car can be made anything between maximum and zero. This characteristic permits the output of the kiln to be adjusted to suit the day by day demand for ware.

6. The more effective transfer of heat to the ware and the ability to stack the ware to a greater height tend to make the length of the kiln less than that of a conventional tunnel kiln designed for the same service.

7. Flexibility of operation is such that even while the kiln is in operation it can be lengthened or shortened either to improve its performance on a given ware or to better adapt it for handling a wide variety of different wares; likewise, the burners can at any time be shifted from place to place to suit the length or to otherwise improve the operation of the kiln.

8. Any car can be held out of service for inspection or repairs without interfering with the operation of the kiln.

9. Maintenance will be low because all metal parts are outside the hot zones and because the heating and cooling of each car takes place evenly and uniformly over its entire interior surface.

10. The cars are all alike and hence can be factory built on a mass production basis. Wheels, axles, bearings, and other metal parts are entirely outside of the hot zones and they can therefore be standard car parts. These manufacturing advantages'tend toward a substantial decrease in cost.

The insulating brick, which plays such a prominent part in the design of this kiln has another valuable characteristic. It has a heat storage capacity of but 6% to 7% of that of the thickness of firebrick which would be required to give the same value of heat insulation. This means that the amount of heat absorbed by the walls in bringing them up to working temperature, and the amount of heat carried away by the walls when a car is removed from the head end of the line, will be but small percentages of the heat absorbed by the ware.

While the foregoing explanation is based on the embodiment of the principles of this invention in a continuous type kiln, I contemplate other types of furnaces as well, including enameling, annealing, billet heating, reheating furnaces and the like. I donot intend to be limited to the details shown and described here-' in, except as set forth in the following claims.

I claim:

1. A furnace of the class described comprising 5 a plurality of portable series connected downdraft heating chambers.

2. A heating furnace comprising a plurality of portable unit chambers and interconnecting duct means for connecting said chambers to form 10 i a continuous passage for gases.

3. In combination with a car type kiln, means for creating a draft through said wares and means for selectively directing said draft upwardly or downwardly through said wares. 15

4. In combination with a car type continuous kiln wherein the wares heated therein pass successively through preheating, firing, and cooling zones, means for creating a draft through said wares and means for selectively directing said 20 draft upwardly through the wares in said cooling zone and downwardly through the wares in said pro-heating and firing zones.

.5. A furnace for progressively heating wares,

said furnace consisting of a train of portable 25 unit heating chambers, means for interconnecting said chambers by ducts and means for passing hot gases of combustion through said connected chambers in succession, wherewith said wares are progressively heated in said cham- 30 bers by adding chambers to one end of said train and removing chambers from the other end of said train.

6. In combination with a furnace for progressively heating wares, said furnace comprising 35 a train of portable unit heating chambers interconnected by ducts to form a continuous passage for a flow of air and waste gases, means for introducing a flow of air at the head end of said train, firingmeans disposed intermediately of 40 said train, and means for by-passing part of said air from a chamber disposed between said air flow introducing means and said firing means, said by-passed air being used for drying purposes and the like. 45

7. In a continuous regenerative kiln of the class described comprising a train of portable interconnected chambers wherein air is introduced into the head end of said train, fuel is introduced intermediate of said train and waste 50 gases are exhausted from the rear end of said train, the ware in said chambers being heated, fired, and cooled by progressing from the rear end to the front end of said train, interconnecting duct means comprising a duct entering each 5 chamber near the top and another duct entering said chamber near the bottom, said lower connecting duct being adapted to register with the upper connecting duct on an adjacent chamber,

and turntable means for reversing each cham- 60 ber as it progresses into the cooling zone whereby the flow of air is conducted upwardly througheach chamber and the flow of gases of combustion is conducted downwardly through each chamber. 65

bottom of said chamber, means for supporting and means for transporting said heating chamber.

9. A portable heating chamber comprising in combination, a jacket carried on a car, a refractory insulating lining in said jacket, a lower the opposite wall of said chamber, and damper means for closing each of said lower ducts.

10. A portable heating chamber of the class described, comprising in combination, a jacket carried on wheels, a lining in said jacket, a lower and an upper inlet duct in one wall of said chamber, a lower and an upper outlet duct in the opposite wall of saidchamber, all of said ducts bending and extending vertically along said walls and terminating intermediate of said walls in such manner that by placing two of said chambers adjacent, said outlet ducts of one chamber register with said inlet ducts of said adjacent chamber, means for sealing the lines of separation between said ducts, and damper means for closing each of said interconnecting ducts.

11. A heating furnace of the class described comprising a plurality of refractory walled chambers, duct means for interconnecting said chambers, said duct means comprising an inlet duct connected into the top of one wall of each chamber and extending downwards along the side of said wall and terminating intermediately of said wall, an outlet duct connected into the bottom of the opposite wall of each chamber and bending upward along the side of said opposite wall and terminating substantially on a horizontal plane with the termination of said inlet duct so that the inlet duct of each chamber registers with the outlet duct of the adjacent chamber, and means for sealing the line of separation between said ducts, said sealing means comprising fluid-filled troughs disposed around said inlet and said outlet ducts near said line of separation, and a Vertically movable collar around each of said inlet ducts, said collar having continuous sealing lips adapted for dipping into both of said troughs simultaneously.

12. In a continuous regenerative muffle kiln of the class described, a portable unit chamber comprising a refractory covered deck mounted on a structural frame and a removable cover structure consisting of a jacket lined with heat insulating material, an inlet duct entering near the top on one side of said structure, an outlet duct disposed near the bottom of said structure, and an inner chamber consisting of refractory walls and roof supported within said cover structure but spaced from said outer cover whereby hot gases of combustion entering said inlet duct flow down over said inner roof, between said spaced apart outer and inner walls, and out through said outlet duct.

13. In a continuous regenerative muffle furnace of the class described, a unit chamber comprising a refractory covered deck mounted on a structural frame, an outer jacket lined with heat insulating material, a refractory roof, an inner refractory wall supported within but spaced from said outer jacket, and inlet and outlet ducts in communication with the space between said inner wall and said lined jacket.

14. In a kiln in which wares are burned on a series of portable decks, means for creating a draft through the ware on each of said decks in succession, said draft flowing in a vertical direction through each deck load of ware.

15. A continuous, regenerative kiln comprising an assembly of heating chambers connected in series, the number of said chambers being adjustable to production demands and to the burning characteristics of different wares.

,16. In a continuous regenerative furnace of the class described, a unit chamber comprising an outer metal jacket, an inner wall of refractory insulation, a layer of fibrous insulation between. said outer jacket and said inner wall, a refractory roof, an inlet duct communicating with the upper portion of said chamber, an outlet ducticommunicating with the lower portion of said chamber, and a structural supporting frame for said chamber.

17. A portable heating chamber comprising a metal jacket lined with insulating material, mounted on a structural supporting frame, a refractory floor supported on said frame, an inlet duct and an outlet duct, both of said ducts being connected into said chamber, said ducts being arranged so that when two of said chambers are placed adjacently, said inlet duct of one chamber can be placed in register with said outlet duct of the other chamber.

18. A unit heating chamber of the class described comprising in combination, a refractory lined vertically disposed cylindrical wall structure, a domed roof, a refractory floor, an inlet duct connected into the upper portion of said chamber, said duct turning downwards along the side of said wall and terminating intermediately of said wall, an outlet duct connected into said chamber near the bottom, said outlet duct turning upwards along the side of said wall 1 and terminating substantially on a plane with the termination of said inlet duct.

19. A unit heating chamber comprising a lower section and a removable cover structure,

an outlet duct connection in said lower section,

and an inlet duct connection in said cover structure.

20. A unit heating chamber consisting of a lower portion comprising a supporting structure, a refractory floor on said structure, a cylindrical 40 wall, and a duct connection into said wall at the bottom, and a removable cover structure comprising a cylindrical wall, a domed roof, and a duct connection, means for supporting said cover structure on said lower portion, and means for sealing the line of separation between said cover and said lower portion against atmospheric leakage.

21. In a continuous kiln, a unit heating chamber consisting of a lower part and a removable cover structure, the lower part comprising a supporting frame, a refractory covered floor, a refractory lined cylindrical wall, and an outlet duct turning upward along said wall, said cover structure comprising a bell shaped, refractory lined casing adapted for registering with said wall of said lower part, and an inlet duct connected into said cover structure, said duct turning downward along said casing, means for removing said structure, and means for sealing the line of separation between the lower part and the cover structure against leakage of gases. 22. A continuous regenerative heating furnace comprising a plurality of unit heating chambers, duct means for connecting said chambers in series, each of said chambers having a lower portion containing a refractory foundation for supporting ware, and a bell shaped upper portion adapted to be removable from said lower portion to permit setting and drawing of ware. 23. A heating furnace of the class described, comprising a plurality of vertically disposed chambers, external ducts connecting the bottom of each of said chambers to the top of an adja cent chamber, and means for passing hot gases of combustion through said chambers, whereby said gases flow downwards through each chamber and upwards through each interconnecting duct.

24. A continuous regenerative kiln, comprising a series of independent metal jacketed, refractory lined, chambers, a series of metal jacketed, refractory lined ducts connecting said chambers in series to form a continuous passage for gases whereby the direction of flow of said gases through each chamber is downward, means for introducing a draft of air for combustion into one end of said kiln, means for introducing fuel into said air circulation in any chamber in the series, and means for exhausting the products of combustion from the other end of said kiln.

25. A continuous regenerative kiln of the class described, comprising a series of unit heating chambers, means for transporting and aligning said chambers, and duct means adapted to register with co-operative means on adjacent chambers.

26. A furnace for progressively heating wares, said furnace consisting of a plurality of portable unit heating chambers, duct means for interconnecting said chambers in series, and means for passing hot gases of combustion through said chambers in succession, whereby said wares are progressively heated in said chambers by adding chambers of unheated ware to one end of said series and removing chambers of heated ware from the other end of said series.

27. A regenerative kiln for progressively firing wares, said kiln comprising a plurality of portable unit heating chambers, duct means for interconnecting said chambers in series to form a continuous passage for gases, means for introducing a flow of air at one end of said series, means for introducing fuel into at least one intermediate unit chamber, and means for exhausting the gases of combustion from the other end of said series, whereby said articles of production are progressively heated, fired, and cooled by adding portable units to the exhaust end of said series and removing chambers of finished products from the air intake end of said series.

28. In a furnace of the class described, a plurality of portable unit heating chambers, said chambers being arranged in alignment, an interconnecting duct fixed in cormnunication with each of said chambers, said ducts being disposed in register with an opening in the adjacent chamber when said chambers are aligned for operation, and means for passing a fiow of gases of combustion through said chambers in succession.

29. The method of progressively heating articles of production in a plurality of portable unit furnaces comprising placing said furnaces in alignment and interconnecting them in series by means of ducts, passing hot gases of combustion through said furnaces in succession, transporting unit furnaces of unheated wares to the furnace assembly, and periodically connecting them to one end of said series, periodically removing furnaces of finished wares and transporting them away from said series.

30. The method of heating, firing and cooling articles of production in a plurality of portable unit furnaces, comprising interconnecting said furnaces in series by means of ducts, introducing air for combustion into a furnace at one end of the series, introducing fuel into a furnace intermediate of the series, exhausting the products of combustion from a furnace at the other end of the series, periodically connecting by the waste gases, then fired, and finally cooled 40 by the air for combustion.

ALLEN M. ROSSMAN. 

